Chinese e-commerce giant Alibaba Group reportedly plans to invest in microblogging service, Sina Weibo, which will bump up the latter's valuation to the tune of US$2 billion to US$3 billion .

A China Business News report on Monday said Alibaba will buy a 15 to 20 percent stake. While both companies had not responded to the rumor, an unnamed source from Sina's middle management told the newspaper the two companies had been discussing the investment on many occasions.

When contacted by ZDNet Asia, an Alibaba spokesperson declined to comment on the report, saying: "As a matter of company policy, we do not comment on rumors or speculation."

The Chinese newspaper speculated Alibaba's investment in Weibo signifies social networking services will be key to its future investments. In 2009, Alibaba had set up an internal social network for Taobao buyers and sellers, but the service did not pick up due to competition from other social networks even after many revamps, China Business News said.

A China Business News report last Saturday said Alibaba's investment will not involve Sina Weibo's parent company Sina. The microblogging service since 2011 has been operating under the name of an independant company, "Beijing Weimeng Chuangke Wangluo Jisu", it said.